The present invention relates to an air distribution duct for distributing air into the cabin of a motor vehicle, and particularly relates to such a device connected to an air-conditioning unit which allows the air, optionally heated or cooled, to be fed in at various locations of the cabin.
With the increased reduction in the noise nuisance produced by the vehicle engine, the air-conditioning unit has become a significant noise source to which the air distribution device contributes. Owing to the transmissivity of the air ducts of said device, the noise of the fan is propagated right into the cabin. Moreover, these ducts are themselves a source of noise resulting from the flow turbulence generated by their architecture.
The known air distribution devices, generally arranged in the dashboard of the vehicle, also have the disadvantage of occupying a considerable amount of space, this space being complicated to manage at the vehicle design stage.
One solution for reducing their space requirement involves the direct use of a metal crossmember of the vehicle, situated inside the dashboard, to route the air, as described in document FR 2 669 885 (Peugeot). However, this solution has the disadvantage of causing heat losses, the materials forming the crossmember having a higher thermal inertia than those used for conventional distribution ducts. The air circulating in the crossmember then takes longer to heat or cool, resulting in a loss of comfort for the occupants of the vehicle.
Another solution involves placing an air distribution duct inside a crossmember, as described in document DE 102 20 025 (Behr), for example. This duct can be made of an inexpensive material and can be supported inside the crossmember by means of rigid supports fastened to the crossmember. The air layer between the duct and the crossmember then serves as a thermal insulator. Such a device allows the crossmember to be structurally rigid, but no noise absorption is provided, with the result that the duct remains a source of noise.
The thermal and acoustic performance of the air distribution device can be improved by adding elastic or semi-rigid supports which absorb the vibrations of the duct, as described in document U.S. Pat. No. 6,715,954 (Benteler). However, the addition of such supports to the periphery of the duct proves costly to achieve and entails a complicated process of assembling the crossmember, the initial shape of which is greatly modified.
There is thus a need to produce at low cost a compact air distribution device which has good thermal and acoustic insulation and is easy to mount in the vehicle.